[MS] Don't escape MS C++ names with \01

It is not needed after LLVM r327734. Now it will be easier to copy-paste
IR symbol names from Clang.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@327738 91177308-0d34-0410-b5e6-96231b3b80d8